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May 02 2012

First Group Field Day

On Saturday 4/29/2012 we had the first field day of the semester. The goal was to begin mapping the trees at HR and to perfect our methods. However we soon discovered that our 5x5 meter plots that had been previously marked with PVC had much more error than we anticipated. To accommodate this we mapped the trees in the corners of 25x25 meter plots because they contained the known survey points.

We managed to get 8 of the 5x5 Meter plots surveyed and ready to document. Also, we have determined a new method to plot the 5x5 meter subplots. Our error came from one main source. When we were measuring the 5x5 subplots we started by marking the perimeter. Once this was done we laid out a string across the plot and measured along the string to mark our subplot points. While the points were 5 meters apart in one direction they were not in the other. The reference string did not provide enough accuracy and would lead to a line of points which fall to the left or the right of where they should fall.

To tackle this problem we purchased a straight line laser that can shoot up to 1000ft. The idea behind this is it will give us a perfectly straight reference line. We will shoot the laser across the plot from one known perimeter point to the next and than proceed to mark the points within the plot that lay on this line. This will hopefully do away with the error that accumulates while measuring along an inaccurate reference line.

At the end of the day we learned allot about our methods and what needs to be improved. This is all a part of field work to design, test, and redesign. Hopefully we will have another group field day soon with corrected subplots allowing much more mapping to be accomplished. I want to thank everyone from the ecosynth team and volunteers who made this day possible. 

Apr 09 2012

First Test of PVC Markers


On Thursday 4/5/2012 Jonathan and I went to HR with 2 other students to attempt to lay out the PVC pipe that will mark the 5x5 meter grid. Our plan was to lay a reference string between 2 of the serveyed points in the 25x25 meter grid. Once this was done we could measure 5 meters along this line with our wooden poles, string, and line levels to help ensure accuracy. We secured a string between the two wooden poles measured at 5 meters We would than insert PVC poles like the ones to the left at these 5 meter marks. However when we finished our first 4 points and came to the known survey point we were anywhere from 10 to 30 cm off. This was too much inaccuracy and we quickly saw that the string connecting the two wooden poles could flex, this being our cause of inaccuracy, we determined we needed a more rigid material to connect the poles. Back at the lab we found some thin metal wire and after attatching this to the wooden poles and retesting the same strategy as before the accuracy was greatly improved, at most we had a 1 to 2 cm innaccuracy with most of the corner points we plotted landing directly on the survey point.

Mar 27 2012

Topography and the Mapping Grid

There has been a new data sheet designed to address the specific needs of the forest we are working with. Because the method for mapping the trees has changed, the data sheets also needed to be altered. We are returning to the previous used method of laying out a 1x1 meter grid within our 5x5 meter grid. Once this is complete the location of the trees will be marked on the graph found on the data sheet. There has also been a "codes" column added to the data sheet to represent trees that may need special attention. This could include a leaning stem, a stem broken below breast hight, or as seen in the picture multiple stems from one trunk forming below breast height. However, before the trees can be mapped the grid must first be sectioned into 5x5 meter squares. Jonathan, fellow students, and I are hoping to get one of the 25x25 meter plots sectioned off so we can begin to test our tree mapping stratgies. We are also tackling the problems we may face concerning drastic elevation changes. In summary we have all of our supplies ready and in bags we just need to find a time to get dirty and see how our ideas work.


 

Mar 21 2012

Tree mapping Technique

There have been many methods for mapping the trees within our 25x25 meter grid that we have identified. The one certatinty we have decided on is the grid must be sectioned into a 5x5 meter grid before we can begin mapping. The picture on the left shows a method found in the field guide Methods For Establishment And Inventory Of Permanent Plots. This method involves usining geometry to determine the exact point of a tree and we thought it could be more accurate and faster than other ideas. However when we went to our forrest to test we discovered that it was not only more tedious but may not improve accuracy by a reasonable amount if at all. The problems arose when we needed to take measurments on unlevel surfaces. It would involve 3 or more people with much instruction and using handfulls of equpment, it was uneffective for our purposes. We plan on going on another test run before the week ends to try another method that will hopefully work for what we need. 

References:

Dallmeier, F. (1992). "Long-term monitoring of biological diversity in tropical forest areas." Methods for establishment and inventory of permanent plots. MAB Digest Series, 11. UNESCO. Paris

Mar 03 2011

New Field Equipment for 3D Forestry

Our new forestry mapping equipment is going to make collecting 3D tree and canopy data a lot easier!

We recently acquired a Trimble GeoXT GPS and TruPulse 360B laser range-finder for use in our forestry field data collection work.  The GeoXT is a high grade mobile-mapping, mobile GIS, GPS unit that offers sub-meter accuracy after post-processing in the lab. 

By itself this would allow us to collect sub-meter (0.5m – 0.7m) accurate positions of tree trunks or other features on the ground.  The TruPulse is used for measuring distances and heights using a built in laser and inclinometer that automatically does all that pesky math that would be needed when using an analog clinometer.  The 360B model has built in Bluetooth communication, which means that with a little configuration in the lab the unit can wirelessly beam positional and height data to the GeoXT.

This combo is used for ‘offset-mapping’ where the user stands in one location with both GPS and laser in hand and by using the laser is able to map to the GPS the XYZ position of other objects that are not nearby (typically less than 200m based on the power of the laser).  For us, this means I can map the position of tree tops in 3D space and automatically record the tree height to the mapping GPS with relative ease and greater precision than when using paper and pencil field notes.  This type of data collection is necessary for the calibration and validation of Ecosynth 3D point clouds, http://ecotope.org/ecosynth/methods/ecology/.

We will roll out this tech in the field in the coming few weeks as we move into the growing season, but in the mean time my initial results suggest that this will be a high-quality approach for mapping the position of tree crowns, a vital and challenging task.

The photo below doesn’t look like much, but it shows a sample of some of this 3D data.  This is an oblique shot looking through a 3D point cloud of the Knoll at UMBC.  The yellow area at the bottom is a digital terrain model of the land underneath the canopy; the blue points are the Ecosynth 3D point cloud of the site; and the red points are 3D points of tree tops and tree base mapped using the GPS  / laser combination.  This screen capture doesn’t do it justice, but trust me when I say that it looks good in 3D!

Hey Evan, are you sure you don’t want to come back to continue the forestry work?

Feb 17 2011

Hexakopter Suspended Payload Tests

How well will a Hexakopter work at carrying an instrument payload suspended several meters below?

That is the question we will be trying to answer in the next few days as we get ready for some work for the Forest Service. The goal is to suspend an instrument payload several meters below the Hexakopter on a light-weight metal cable. The payload will weigh about 1.25 lb (0.56 kg) and needs to be far enough away from the Hexa to avoid the effects of downward prop wash. The payload and Hexa will be flying through smoke and we want the instruments to be unaffected by the Hexa itself.

I purchased some 1/16" (~1.6 mm) braided metal cable, some ferrules and some clips from the local hardware store to build the suspension system. I am going to use a 'calibrated' water bottle in place of the instrument payload for weight.

I am going to test:

1) At what distance below the Hexakopter will the effects of prop wash be non-existent / negligible? This will be done in the field by flying a Hexa above a pole with flagging tape on it. This distance will be referred to as X meters.

2) Can the Hexakopter fly in manual and auto mode with a 1.25 lb payload suspended at X meters from a 1/16” metal cable? This will be tested by performing take-off, manual flying, auto-hold, auto-waypoint flying, and landing with the payload attached. Results will suggest total success or a range of flight performance. It is expected that wind will play a significant factor.

3) How long can the Hexakopter fly with the payload attached? This will be tested by first getting the Hexa to altitude with payload and letting it to hover until the battery is at the minimum safe capacity. Then, with a fresh battery installed, it will be tested by flying a simple ‘back and forth’ route over the flight area to simulate increase battery demand.  It is expected that there is a great potential for pendulum affects to occur during flight.

Stay tuned for some results!

UPDATE: I forgot, one of the main Hexakopter videos shows Holger doing his insane Hexa flying witha 1kg soda bottle suspended from below.

http://www.youtube.com/watch?v=gvH2f-AewX8&t=8m0s

Oct 29 2010

Field Work Progress Report

So far this week I was able to put in a couple of hours to continue the field work that was initially laid out by me and Noam Raffel over the Summer of 2010. The tree plots of Herbert Run near completion with what appears to be perhaps another week or two’s worth of work, barring any complications with weather, etc. The leaves are changing quickly at this site as can be seen from the bi-weekly photos taken by Jonathan and the team so this has made it exceptionally apparent that it is now or never (at least not until spring) for the field work.

The measurements are coming along nicely especially since we began using the 3P mode on the hypsometer to limit the distance we have to stand from the tree for accurate assessments. This function works more similar to a clinometer than a standard range finder as 2PL mode does. Several plots worth of trees should be measured using both modes to ensure the consistency of the data.

 

Diagram of Plots

Red = Un-measureable due to new fence

Green = Tree Data collected

Yellow = Remaining plots

 

 

 

 

Check back to this blog for weekly updates on the progress of our field work and comparisons to the data we pull from our photos!